[Kea-users] How to best update the KEA configuration on a HA hot-standby KEA setup

[Veronique Lefebure]

I am wondering whether it is not more efficient to perform a
"config-write" followed by a "config-reload"
rather than a "config-set" ?

________________________________
From: Kea-users <kea-users-bounces at lists.isc.org> on behalf of Veronique Lefebure <Veronique.Lefebure at cern.ch>
Sent: Thursday, November 17, 2022 9:19 AM
To: Dan Oachs <doachs at gac.edu>
Cc: kea-users at lists.isc.org <kea-users at lists.isc.org>
Subject: Re: [Kea-users] How to best update the KEA configuration on a HA hot-standby KEA setup

Hi,

We don't use any database for storing the KEA configuration: we use plain json configuration files.
We need to update the configuration very regularly because we allow only known clients (pre-registered mac addresses), hence the list of host-reservations is quite volatile.

Véronique
________________________________
From: Dan Oachs <doachs at gac.edu>
Sent: Wednesday, November 16, 2022 6:31 PM
To: Veronique Lefebure <Veronique.Lefebure at cern.ch>
Cc: kea-users at lists.isc.org <kea-users at lists.isc.org>
Subject: Re: [Kea-users] How to best update the KEA configuration on a HA hot-standby KEA setup

I am curious why you are updating the config every 5 minutes.   We used to do that with our old DHCP server, but with Kea we moved to storing reservations in a database.  That way we rarely need to make changes to the actual Kea configuration that would necessitate a reload of the config.

--Dan


On Wed, Nov 16, 2022 at 10:27 AM Veronique Lefebure <Veronique.Lefebure at cern.ch<mailto:Veronique.Lefebure at cern.ch>> wrote:
Hi,

When running KEA on one single server, (no HA), and updating the KEA dhcp configuration file every 5 minute, using "config-set"
https://kea.readthedocs.io/en/latest/arm/ctrl-channel.html?highlight=config-set#the-config-set-command ,
we can see that KEA does not reply to the DHCP requests during 30-35 seconds while "config-set" is running.

Is it expected ?
If yes, if we add a second server in a HA hot-standby mode, can we expect it to answer to the DHCP requests while the first server is busy with config-set ?
If yes, we need to update the second server asynchronously with respect to the first one, else they would both be busy with "config-set" at the same time.

I would be interested to know how people are updating the KEA DHCP configuration in a HA hot-standby setup.

Thanks,
Veronique

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